The present invention relates to the classification of golf club shafts in the production of matched sets of golf clubs, and more particularly to determining the frequency of individual golf club shafts and utilizing such frequency determinations to produce frequency modulated matched sets of golf clubs.
As presently manufactured, golf club sets are matched by utilizing static determinations including shaft length, overall club weight, swing weight, and manufacturer's designation of shaft flex. The flex of shaft is an arbitrary and relative designation and varies widely within specific flex designations. Generally, flex designation "X" stands for an extra stiff shaft, "S" for a stiff shaft, "R" for a regular shaft, "A" for a semiflexible shaft, and "L" for a lady or flexible shaft.
Many flex designations are determined by utilizing a flex board which measures statically the deflection of a shaft under the influence of a predetermined test weight secured to the tip end of a shaft anchored at the butt end. Actually, this procedure does not measure the flex or elasticity of the shaft which varies according to cross section, heat treating processes, metal composition and other factors. Hence, deflection is the only shaft characteristic measured by this procedure.
The flexibility of a golf club shaft plays a prime role in producing desirable golf shots. In connection with this role, it is believed desirable that during a golf shot the club shaft travel through a specific number of cycles of deflection from the start of the downswing of the club to the point of impact with the ball. Ultimately, when the club head contacts the ball, it is desirable that the shaft be in an undeflected position which positions the head at its point of maximum velocity. Hence, impact occurs at the point of maximum velocity of the club head which produces the ideal condition for a superior golf shot. Assuming the same swing or pass is placed on the club by the golfer, the flex of the shaft affects the golf shot as follows. If the shaft is too stiff, the club head ultimately passes through the point of maximum velocity prior to contacting the ball. Contact occurs later and the velocity of the club head at that point in time is substantially less. Conversely, if the shaft is too flexible, contact with the ball occurs prior to the club head reaching its maximum acceleration. In each instance, the distance of the golf shot is less than possible under ideal conditions of shaft flex.
U.S. Pat. No. 2,822,174, granted Feb. 4, 1958, relates to matched golf clubs including matched sets of golf club shafts. According to the disclosure, three essential factors of each shaft are correlated in predetermined manner throughout the woods and irons, and these factors include length of shaft, weight of shaft and shaft stiffness. However, the weight method of determining relative stiffness, as disclosed therein, is contrary to the instant invention.